MAGIC reveals a complex morphology within the unidentified gamma-ray source HESS J1857+026

Abstract

HESS J1857+026 is an extended TeV gamma-ray source that was discovered by H.E.S.S. as part of its Galactic plane survey. Given its broadband spectral energy distribution and its spatial coincidence with the young energetic pulsar PSR J1856+0245, the source has been put forward as a pulsar wind nebula (PWN) candidate. MAGIC has performed follow-up observations aimed at mapping the source down to energies approaching 100 GeV in order to better understand its complex morphology. HESS J1857+026 was observed by MAGIC in 2010, yielding 29 hours of good quality stereoscopic data that allowed us to map the source region in two separate ranges of energy. We detected very-high-energy gamma-ray emission from HESS J1857+026 with a significance of $12\sigma$ above $150$ GeV. The differential energy spectrum between $100$ GeV and $13$ TeV is well described by a power law function $dN/dE=N_0(E/1\text{TeV}{)}^{-\Gamma }$ with $N_0=(5.37\pm 0.44_{stat}\pm 1.5_{sys})\times 10^{-12}({\text{TeV}}^{-1}{\text{cm}}^{-2}$ ${\text{ s}}^{-1})$ and $\Gamma =2.16\pm 0.07_{stat}\pm 0.15_{sys}$, which bridges the gap between the GeV emission measured by Fermi-LAT and the multi-TeV emission measured by H.E.S.S.. In addition, we present a detailed analysis of the energy-dependent morphology of this region. We couple these results with archival multi-wavelength data and outline evidence in favor of a two-source scenario, whereby one source is associated with a PWN, while the other could be linked with a molecular cloud complex containing an HII region and a possible gas cavity.

9 pages, 6 figures. Accepted for publication in A&A

References in corpus (14)

• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• The VLA Galactic Plane Survey
• Kinematic Distances to Molecular Clouds identified in the Galactic Ring Survey
• Implementation of the Random Forest Method for the Imaging Atmospheric Cherenkov Telescope MAGIC
• HESS VHE Gamma-Ray Sources Without Identified Counterparts
• Resolution of the Distance Ambiguity for Galactic HII Regions
• Milky Way Kinematics: Measurements at the Subcentral Point of the Fourth Quadrant
• Unfolding of differential energy spectra in the MAGIC experiment
• The Molecular Properties of Galactic HII Regions
• PSR J1856+0245: Arecibo Discovery of a Young, Energetic Pulsar Coincident with the TeV Gamma-ray Source HESS J1857+026
• Fermi-LAT constraints on the Pulsar Wind Nebula nature of HESS J1857+026
• The H.E.S.S. Galactic Plane Survey - maps, source catalog and source population
• Galactic sources of E>100 GeV gamma-rays seen by Fermi telescope
• Cold Atomic Gas in the CGPS and Beyond

Cited by in corpus (14)

• The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula
• The 2HWC HAWC Observatory Gamma Ray Catalog
• Search for extended sources in the Galactic Plane using 6 years of Fermi-Large Area Telescope Pass 8 data above 10 GeV
• IceCube Search for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae
• Search for TeV Gamma-Ray Emission from Point-like Sources in the Inner Galactic Plane with a Partial Configuration of the HAWC Observatory
• Using Interstellar Clouds to Search for Galactic PeVatrons: Gamma-ray Signatures from Supernova Remnants
• Expectation on Observation of Supernova Remnants with the LHAASO Project
• Multiwavelength constraints on the unidentified Galactic TeV sources HESS J1427$-$608, HESS J1458$-$608, and new VHE $\gamma$-ray source candidates
• MAGIC and Fermi-LAT gamma-ray results on unassociated HAWC sources
• Chandra observations of the HII complex G5.89-0.39 and TeV gamma-ray source HESSJ1800-240B
• HESS J1858+020: A GeV-TeV source possibly powered by CRs from SNR G35.6-0.4
• Quantitative constraint on the contribution of resolved gamma-ray sources to the sub-PeV Galactic diffuse gamma-ray flux measured by the Tibet ASγ experiment
• Radio study of HESS J1857+026. Gamma-rays from a superbubble?
• Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk